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Biomedical subjects

A Johnson

Publications and source records attributed to A Johnson.

At least 613 records · Page 34Linked to original sources
PubMed1980

HLA antigens in schizophrenia:differences between patients with and without evidence of brain atrophy.

A survey of 14 published studies found no consistent association between specific HLA antigens and schizophrenia. Since these studies lacked diagnostic or biological criteria, an investigation was undertaken using recognized diagnostic criteria and CT scan findings. Typing for HLA antigens at loci A, B and C was carried out on 130 patients. Among 92 black schizophrenic patients there was an increase of HLA-A2 which remained significant even after correcting for the number of antigens studied. When the patients for whom CT scans were available were divided according to the presence or absence of evidence of brain atrophy, there was an increase of A2 in the black schizophrenic patients without evidence of atrophy, which remained significant after multiplying by the number of antigens studied. However, there was no significant increase of A2 in those with evidence of atrophy. Similar trends held for the white population but they failed to reach significance. The need for HLA studies on biologically defined groups of schizophrenic patients is stressed.

Adult↗
PubMed1979

Hereditary hemochromatosis. Phenotypic expression of the disease.

Previous studies have shown that hemochromatosis is an inherited, autosomal-recessive disease and that the gene is closely linked to the HLA locus on chromosome 6. We obtained a lod score for linkage of +9.8 for a recombination fraction of 0.0 and a gene frequency of 0.056, the frequency estimated in this population. We studied the phenotypic expression of the disease in 261 members of 10 pedigrees. In heterozygotes over 20 years of age, there was an intermediate increase in transferrin saturation and a limited increase in hepatic iron but no clinical manifestations. In male heterozygotes, the average amount of iron in the liver increased from about 0.2 to 1.3 g. Abnormal homozygotes accumulated iron progressively with time, with men accumulating about 18 g in the liver. All measurements of iron status were increased in abnormal homozygotes. Hemochromatosis is inherited as an autosomal-recessive disease, with partial biochemical expression in heterozygotes.

Adolescent↗
PubMed1979

The electrocardiogram in asymmetric septal hypertropy.

Electrocardiograms and echocardiograms in 44 patients with asymmetric septal hypertrophy were reviewed. Patients with asymmetric septal hypertrophy had incidences of left ventricular hypertrophy (33 percent; 16/44) and left atrial hypertrophy (25 percent; 11/44) by ECG that were less than in a group of patients with significant aortic stenosis (70 percent [31/44] and 64 percent [28/44], respectively). Left ventricular hypertrophy on the ECG was associated with a greater septal-posterior wall thickness ratio in asymmetric septal hypertrophy. A small Q wave in lead V4 or a ratio of the R-wave to the S-wave amplitude (R/S ratio) of greater than 0.20 in lead V1 was found in 14 of 44 patients with asymmetric septal hypertrophy but in no patients with aortic stenosis. The mean corrected Q-T interval (Q-Tc) of patients with asymmetric septal hypertrophy was prolonged, and the mean Q-Tc of patients with aortic stenosis was normal. The distinctive findings of an R/S ratio of more than 0.2 in lead V1 and Q waves in lead V4 in asymmetric septal hypertrophy have clinical significance, and the prolonged Q-T interval may relate to sudden death.

Adult↗
PubMed1979

Genetic linkage between hereditary hemochromatosis and HLA.

A large Mormon pedigree of a proband with hemochromatosis was studied, using transferrin saturation as the quantitative phenotypic trait. The analysis indicated that the inheritance of hemochromatosis was recessive, with partial expression in some heterozygotes. The lod score of 6.88 (theta = .0) was strongly indicative of linkage between the hemochromatosis locus and the human major histocompatibility (HLA) loci.

Chromosome Mapping↗
PubMed1978

Thryo-endocrine pathology, obstetric morbidity and schizophrenia: survey of a hundred families with a schizophrenic proband.

This preliminary communication reports that the mothers of 104 schizophrenic patients had: (1) a significantly higher incidence of thyroid disease than a carefully matched control group; (2) significantly more abortions, still-births and greater infant mortality. The findings and possible relevance of thyroid disease to schizophrenia are discussed. Three prospective studies currently in progress are outlined.

Abortion, Spontaneous↗
PubMed1978

Mechanism of action of the cro protein of bacteriophage lambda.

The mechanism of action of cro protein was probed by measuring its ability to protect DNA against methylation by dimethyl sulfate and its effect on transcription in vitro. The cro protein binds to the same three sites in the right operator (OR) of bacteriophage lambda DNA as does the lambda repressor. Dimethyl sulfate protection experiments reveal major groove contacts for both proteins, and cro protein protects from methylation a subset of those purines protected by lambda repressor. These experiments also show that the relative affinity of these two proteins for the three operator sites is different: whereas lambda repressor binds with an affinity OR1 greater than OR2 greater than OR3, the order for cro protein is OR3 greater than (OR1, OR2). As predicted by these results, cro protein, like the lambda repressor, blocks in vitro transcription of cI and cro from the two divergent promoters that overlap OR. Also as predicted, transcription of cI is turned off at lower cro protein concentrations than is transcription of cro, whereas the opposite order of repression is obtained with lambda repressor. These results describe the molecular mechanism of cro protein action and show that two regulatory proteins can bind to the same three adjacent sites in DNA with markedly different consequences.

Base Sequence↗
PubMed1978

Diastolic left ventricular pressure-volume and stress-strain relations in patients with valvular aortic stenosis and left ventricular hypertrophy.

Left ventricular (LV) chamber and myocardial stiffness were determined in 17 patients, four subjects with normal LV function and 13 subjects with valvular aortic stenosis and concentric myocardial hypertrophy, using simultaneous catheter micromanometry and LV cineangiography. Pressure (P), volume (V), and wall thickness (h) were measured. Variability in both chamber and myocardial stiffness parameters was found with five of the aortic stenosis patients (Group 1, left ventricular end-diastolic pressure = 15 +/- 2 (SEM) mm Hg) exhibiting normal values for end-diastolic dP/dV and dP/dV/V, for chamber stiffness constants (a,a') derived from P-V and normalized P-V relations, respectively, for end-diastolic myocardial elastic stiffness (ES or EE, where S = spherical model and E = ellipsoidal model) at the midwall of the minor axis circumference, and for the myocardial stiffness constants (KS or KE) of the circumferential stress-strain relation. Eight other patients with aortic stenosis (Group II, left ventricular end-diastolic pressure = 20 +/- 3 (SEM) mm Hg) exhibited significant increases in end-diastolic dP/dV,dP/dV/V,ES and EE and a tendency for increase in the chamber stiffness constants (a,a') and myocardial stiffness constants (KS, KE). These observations suggest that concentric increase in muscle mass (increase in wall thickness/minor axis radius ratio and wall volume/chamber volume ratio) is an important determinant of elevated mid- and late diastolic pressures in patients with valvular aortic stenosis, while concurrently mitigating increases in both systolic and diastolic wall stress. In some patients with aortic stenosis, however, diastolic filling pressures are elevated more severely, not only as a result of concentric hypertrophy, but also in response to augmented muscle stiffness. Reversibility of increased ventricular diastolic stiffness and elevated filling pressures was documented as concentric hypertrophy regressed post-aortic valve replacement in one patient, suggesting that fibrosis is not invariably the cause of enhanced myocardial stiffness in this secondary and compensatory form of hypertrophy.

Adult↗